print.c

#ifndef _PRINT_C_ /* -*- linux-c -*- */
#define _PRINT_C_

#include <linux/config.h>

#include "io.c"

/** @file print.c
 * @addtogroup print Print Buffer
 * Print Buffer Functions.
 * The print buffer is for collecting output to send to the user daemon.
 * This is a per-cpu static buffer.  The buffer is sent when
 * _stp_print_flush() is called.
 *
 * The reason to do this is to allow multiple small prints to be combined then
 * timestamped and sent together to stpd. It could flush automatically on newlines,
 * but what about stack traces which span many lines?  So try this and see how it works for us.
 * @{
 */

/** Size of buffer, not including terminating NULL */
#define STP_PRINT_BUF_LEN 8000

static int _stp_pbuf_len[NR_CPUS];

#ifdef STP_NETLINK_ONLY
#define STP_PRINT_BUF_START 0
static char _stp_pbuf[NR_CPUS][STP_PRINT_BUF_LEN + 1];

void _stp_print_flush (void)
{
        int cpu = smp_processor_id();
        char *buf = &_stp_pbuf[cpu][0];
        int len = _stp_pbuf_len[cpu];

        if (len == 0)
                return;

        if ( app.logging == 0) {
                _stp_pbuf_len[cpu] = 0;
                return;
        }
        
        /* enforce newline at end  */
        if (buf[len - 1] != '\n') {
                buf[len++] = '\n';
                buf[len] = '\0';
        }
        
        send_reply (STP_REALTIME_DATA, buf, len + 1, stpd_pid);
        _stp_pbuf_len[cpu] = 0;
}

#else /* ! STP_NETLINK_ONLY */
/* size of timestamp, in bytes, including space */
#define TIMESTAMP_SIZE 19
#define STP_PRINT_BUF_START (TIMESTAMP_SIZE + 1)
static char _stp_pbuf[NR_CPUS][STP_PRINT_BUF_LEN + STP_PRINT_BUF_START + 1];

/** Send the print buffer now.
 * Output accumulates in the print buffer until this is called.
 * Size is limited by length of print buffer, #STP_PRINT_BUF_LEN.
 */

void _stp_print_flush (void)
{
        int cpu = smp_processor_id();
        char *buf = &_stp_pbuf[cpu][0];
        char *ptr = buf + STP_PRINT_BUF_START;
        struct timeval tv;

        if (_stp_pbuf_len[cpu] == 0)
                return;
        
        /* enforce newline at end  */
        if (ptr[_stp_pbuf_len[cpu]-1] != '\n') {
                ptr[_stp_pbuf_len[cpu]++] = '\n';
                ptr[_stp_pbuf_len[cpu]] = '\0';
        }
        
        do_gettimeofday(&tv);
        scnprintf (buf, TIMESTAMP_SIZE+1, "[%li.%06li] ", tv.tv_sec, tv.tv_usec);
        buf[TIMESTAMP_SIZE] = ' ';
        relayapp_write(buf, _stp_pbuf_len[cpu] + TIMESTAMP_SIZE + 2);
        _stp_pbuf_len[cpu] = 0;
}
#endif /* STP_NETLINK_ONLY */

/** Print into the print buffer.
 * Like printf, except output goes to the print buffer.
 * Safe because overflowing the buffer is not allowed.
 * Size is limited by length of print buffer, #STP_PRINT_BUF_LEN.
 * 
 * @param fmt A printf-style format string followed by a 
 * variable number of args.
 * @sa _stp_print_flush()
 */

void _stp_printf (const char *fmt, ...)
{
        int num;
        va_list args;
        int cpu = smp_processor_id();
        char *buf = &_stp_pbuf[cpu][STP_PRINT_BUF_START] + _stp_pbuf_len[cpu];
        va_start(args, fmt);
        num = vscnprintf(buf, STP_PRINT_BUF_LEN - _stp_pbuf_len[cpu], fmt, args);
        va_end(args);
        if (num > 0)
                _stp_pbuf_len[cpu] += num;
}

/** Print into the print buffer.
 * Use this if your function already has a va_list.
 * You probably want _stp_printf().
 */

void _stp_vprintf (const char *fmt, va_list args)
{
        int num;
        int cpu = smp_processor_id();
        char *buf = &_stp_pbuf[cpu][STP_PRINT_BUF_START] + _stp_pbuf_len[cpu];
        num = vscnprintf(buf, STP_PRINT_BUF_LEN -_stp_pbuf_len[cpu], fmt, args);
        if (num > 0)
                _stp_pbuf_len[cpu] += num;
}

/** Write a C string into the print buffer.
 * Copies a string into a print buffer.
 * Safe because overflowing the buffer is not allowed.
 * Size is limited by length of print buffer, #STP_PRINT_BUF_LEN.
 * This is more efficient than using _stp_printf() if you don't
 * need fancy formatting.
 *
 * @param str A C string.
 * @sa _stp_print
 */

void _stp_print_cstr (const char *str)
{
        int cpu = smp_processor_id();
        char *buf = &_stp_pbuf[cpu][STP_PRINT_BUF_START] + _stp_pbuf_len[cpu];
        int num = strlen (str);
        if (num > STP_PRINT_BUF_LEN - _stp_pbuf_len[cpu])
                num = STP_PRINT_BUF_LEN - _stp_pbuf_len[cpu];
        strncpy (buf, str, num+1);
        _stp_pbuf_len[cpu] += num;
}

/** Clear the scratch buffer.
 * This function should be called before anything is written to 
 * the scratch buffer.  Output will accumulate in the buffer
 * until this function is called again.  
 * @returns A pointer to the buffer.
 */

char *_stp_print_clear (void)
{
        int cpu = smp_processor_id();
        _stp_pbuf_len[cpu] = 0;
        return &_stp_pbuf[cpu][STP_PRINT_BUF_START];
}

#include "string.c"

/** Write a String into the print buffer.
 * Copies a String into a print buffer.
 * Safe because overflowing the buffer is not allowed.
 * Size is limited by length of print buffer, #STP_PRINT_BUF_LEN.
 * This is more efficient than using _stp_printf() if you don't
 * need fancy formatting.
 *
 * @param str A String.
 * @sa _stp_print
 */

void _stp_print_string (String str)
{
        if (str->len)
                _stp_print_cstr (str->buf);
}

/** Write a String or C string into the print buffer.
 * This macro selects the proper function to call.
 * @param str A String or C string (char *)
 * @sa _stp_print_cstr _stp_print_string
 */

#define _stp_print(str)                                                 \
        ({                                                              \
          if (__builtin_types_compatible_p (typeof (str), char[])) {    \
                  char *x = (char *)str;                                \
                  _stp_print_cstr(x);                                   \
          } else {                                                      \
                  String x = (String)str;                               \
                  _stp_print_string(x);                                 \
          }                                                             \
  })

/** @} */
#endif /* _PRINT_C_ */